Washing machine



I Dem 22,1970 TosHlKAzu oHNlsHl ETAL .3,543,515

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WASHING MACHINE 7 Sheets-Sheet 5 Filed oct. so, 196e F/G. a

INVENTOR @WAI/wl, ,lv/mel WASHING MACHINE Filed oct. so, 196e 7sheets-sheet v INVENTOR 01W/wf, n,

United States Patent O 3,548,615 WASHING MACHINE Tosliikazu Ghnishi,Hiroki Utsumi, Toru Tazawa, Sigeto Yamane, and Katsumasa Matsuura,Hitachi-shi, Japan, assgnors to Hitachi, Ltd., Tokyo, Japan, acorporation of Japan Filed Oct. 30, 1968, Ser. No. 771,919 `Claimspriority, application Japan, Nov. 1, 1967,

ft2/69,862; Nov. 10, 1967, 4t2/71,992

Int. Cl. D06f 37/22 U.S. Cl. 68-23.1 9 Claims ABSTRACT F THE DISCLOSUREA drum-type washing machine capable of performing programmed operationsranging from a clothing operation to a spinning operation automatically,wherein a motor for driving a drum is shifted from a low rate of speedto a high rate of speed under the control of vibration detecting meansprovided on the drum and the drum is accelerated to a higher rate upondetecting the fact that a clothing in the drum is distributed evenlywith respect to the center of rotation of said drum, whereby anexcessively large vibration of the drum is prevented.

This invention relates to a drum-type ywashing machine and moreparticularly to a drum-type washing machine which is so designed thatthe vibration of a clothing accommodating drum is minimized while therotating speed of said drum is being accelerated and `after the rotatingspeed has been accelerated to the high speed rotation by changing overthe rotating speed of said drum to high speed rotation when theamplitude of the drum vibration is within a tolerable range over apredetermined period of time.

In the operation of a drum-type washing machine of the type which isprovided with a drum rotating about a horizontal shaft or a shaftinclined at a predetermined langle with respect to a horizontal planeand which is operated by a process comprising placing a clothing in thedrum, charging a cleaning liquid in said drum, rotating the drum at alow speed for rolling the clothing therein thereby washing said clothingand rotating the drum at a high speed lwith a drain valve opened toeffect centrifugal spinning, the drum tends to undergo an excessivelylarge vibration `while the rotating speed of said drum is beingaccelerated and after the rotating speed has been accelerated to thehigh speed rotation due to uneven distribution of the clothing in thedrum.

Such vibration has not only caused a noise but also brought about thedisadvantage that vibrating members `are damaged by collision withstationary members, such as an outer frame. For this reason, it has beenusual to repeat the steps of interrupting the acceleration of dr-umhalfway upon occurrence of an excessive vibration, redueing the rotatingspeed of the drum to the low speed rotation, continuing the low speedrotation for a predetermined period and then accelerating the drum againto high speed. According to this method, however, the probability of theclothing being distributed in the drum uniformly with respect to thecenter of rotation while acceleration to a high speed rotation is soslim that an excessively large vibration occurs frequently in the courseof acceleration and transition to a high speed rotation can beaccomplished only after repeated acceleration and deceleration.Therefore, transition from the low speed rotation to the high speedspinning step cannot be attained smoothly.

There have also been proposed to suppress the vibration generated, byadding a large mass to a water tank pro- ICC vided containing the drum,but this method is quite superficial and passive.

Because in this method a technical consideration is given only as to howrationally the vibration generated can be suppressed, after Iacceptingthe vibration, resulting from uneven distribution of clothing in thedrum, as an inevitable phenomenon. The suppression of a vibrationgenerated is not a fundamental solution to the problem of eliminatingthe cause of vibration, while the provision of an additional mass fxedlyor automatically is in no Way desirable from the standpoint ofstructure, strength and cost.

The present invention has been achieved based on the discovery, throughexperiments, that the vibration of drum would be extremely smalltransition of the drum rotation to a high speed rotation could beattained smoothly `without generating an excessively large vibrationwhen a clothing in the drum is distributed symmetrically evenly Withrespect to the center of rotation of the drum in the low speed rotationof the drum and the rotation of the drum is shifted from low speedrotation to high speed rotation under such condition.

An object of the present invention is to prevent an excessively largevibration occurring while the rotating speed of said drum is beingaccelerated and after the rotating speed has lbeen accelerated to thehigh speed rotation.

Another object of the invention is to provide highly sensitive detectingmeans for detecting the timing of shifting the drum from low speedrotation to high speed rotation.

Still another object of the invention is to provide a washing machinewhich is so constructed that an excessively large vibration sporadicallyoccurring during acceleration of the drum from low speed rotation tohigh speed rotation can be damped effectively.

Still another object of the invention is to provide detecting means fordetecting the timing of transition from low speed rotation to high speedrotation at low costs.

Other objects and advantages of the present invention will becomeapparent from the following detailed description lwhen taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a front elevation of a drum-type washing machine according tothe present invention, with a front panel broken away to show amechanism interior of the machine;

FIG. 2 is a vertical sectional view of the washing machine;

FIG. 3 is a wiring diagram of the drum-type washing machine;

FIG. 4 is a diagram illustrating the operation program of the drum-typewashing machine;

FIG. 5 is a detailed view of vibration detecting means;

FIG. 6 is a wiring diagram of the control circuit used in the drum-typelwashing machine;

FIG. 7a is a detailed view of another form of the vibration detectingmeans;

FIG. 7b is a fragment-ary enlarged view of the vibration detecting meansshown in FIG. 7a;

FIG. 8 is a wiring diagram of another form of the control circuit;

FIG. 9 is a diagram showing a vibration wave form of the drum; and

FIG. 10 is a vibration characteristic chart.

Referring to the drawings, a lbox-shaped outer frame 1 has stays 2provided across the upper portions of the inner surface of the sidewalls thereof and each stay 2 has seimspherical indents 3 formed thereinat two places. In each of the semispherical indents 3 is slidablymounted a piece 5 which has a semispherical convexed surface and isconnected to a bolt 4. The bolt 4 extends downwardly through the stay 2,with a spring seat 6 threadably mounted on the lower end portionthereof. A suspension coil spring 7 has the upper end thereof fitted onthe spring seat 6 and the lower end thereof anchored to the side wall ofa cylindrical outer tank 8, thereby suspending said outer tank.

On the back side of the outer tank 8 is provided a bearing cylinder 9which is extending through an end wall member 10 and secured to theouter tank 8. The bearing cylinder 9 has ball bearings 11 disposedtherein through which a drum shaft 12 is journaled. A washingaccommodating drum 14 is fixedly connected to the inner end of the drumshaft 12 through a liange member 13, while a pulley 16 is fixedlymounted on the outer end of the drum shaft by means of a key 15.

The drum 14 has a number of apertures 17 perforated through theperipheral wall thereof for the passage of Water therethrough in theprocess of spinning. The drum 14 also has a plurality of inwardlyprojecting baffles 18 secured to the inner wall surface thereof by bolts19 extending axially across the drum.

The front end face of the outer tank 8 is covered with a front cover 20which is secured to the outer tank through a packing 21 and said frontcover 20 has an opening in the central portion thereof for throwing aclothing therethrough. The peripheral edge of the opening is connectedto the peripheral edge 23 of a clothing inlet opening 24, formed in thefront wall of the outer frame 1, by means of a flexible rubber bellows22. The clothing inlet opening 24 is closed by a door 25 made of atransparent plastics.

Arms 26 and 27 are connected to the bottom of the outer tank 8 bywelding and motors 28 and 29 are fixed to the lower ends of therespective arms. The driving shaft 30 of the motor 29 has a large pulley32 loosely mounted thereon through a spring clutch 31 and said largepulley 32 is in turn operatively connected to a small pulley of theother motor 28 through a V-belt (not shown) The driving shaft 30 alsohas a small pulley 33 keyed thereon and a V-belt 34 is engaged aroundsaid small pulley 33 and the aforesaid pulley 16 fxedly mounted on thedrum shaft 12.

The motor 28 is operatively connected to a pump 35 to drive the same,said pump 35 being connected to the bottom of the outer tank. The pump35 is driven from the motor 28 during the process of washing operationto circulate a washing water retained in the outer tank 8.

Extending slantingly downwardly from the outer tank 8 are frictionplates 37 and 38. These friction plates are each clamped between frontand rear friction members 40, 41 and damp a vibration of the outer tank8 in engagement with said friction members. The friction members 40, 41are supported by respective supporting springs 39 fixed to the outerframe.

At the upper portion of the outer frame 1 are provided a filling fiange42 for connection to an external faucet and a filling solenoid valve 43in communication with said filling fiange. The outlet of the fillingsolenoid valve 43 is communicated with the upper portion of the outertank 8 through a filling tube 44.

The filling solenoid valve 43 is operated under the control of apressure switch 45 which is actuated by the water level in the outertank 8 and is communicated with the bottom portion of the outer tankthrough a pipe 46.

Reference numeral 47 designates a timer which is so designed that onceit has been set at a starting position, a programmed opration is carriedout automatically by the action of a timer motor, accommodated therein,in accordance with a timer cycle chart to be described later. Theoperation is started by manually operating a knob 48.

Reference numeral 49 designates a vibration detector fitted to a portionof the stay 2 and the detailed structure of said vibration detector isshown in FIG. 5. Reference numeral 50 designates a box in which ishoused means for controlling the rate of rotation of the drum inresponse to a signal from the vibration detector 49. The detailed wiringof the control means 50 is shown in FIG. 6.

Now, the structure of the vibration detector 49 will be described indetail with reference to FIG. 5. The vibration detector 49 comprises avibration transmitting rod 52 connected integrally with the piece 5having a semispherical convexed surface. The vibration transmitting rod52 has connected to the lower end thereof an electrode box 53. In theelectrode box 53 is disposed a movable contact 55 which is normally heldcentrally of the box under the biasing forces of return springs 54.Fixed contacts 56 are provided on the outer frame side at locationsopposite to the opposite ends of the movable contact 5S respectivelywith a distance S therebetween. The movable contact 55 and the fixedcontacts 56 are electrically connected with the control means by leadwires 57, 58 as shown in FIG. 6.

Referring to FIG. 6, a voltage from a commercial power source is droppedby a transformer 60, rectified and smoothened by a diode 61 and acondenser 62, and impressed across the movable contact and the fixedcontacts through resistors 63, 67 and 68. A condenser 64 is connected inparallel to both contacts, so that a charging voltage of said condenser64 is supplied to the base of a transistor 65 through a resistor 69.

Upon energization of the transistor 65, the base potential of atransistor 66 rises due to a voltage drop of a resistor 70, whereby saidtransistor 66 is energized and accordingly the exciting coil of a relay72 is excited. The exciting coil serves as a pole changer for the motor28 shown in the circuit diagram of FIG. 3.

A cam switch 73 is closed under the control of a timer motor 74 onlywhen the program enters the spinning process.

Next, the operation of the drum-type washing machine constructed asdescribed above will be described with reference to the circuit diagramof FIG. 3 and the timer cycle chart of FIG. \4.

Referring first to FIG. 3, reference numerals 73, 81, 82, 83, 84, 85, 86and 87 designate cam switches controlled by a series of cams provided onthe shaft of a timer motor 89, and the configurations of the cams of therespective cam switches are so selected that they will contact thelateral thick lines in the program chart of FIG. 4 respectively. A doorswitch 91 which is adapted to be closed only when the door 25 is closed,the cam switch 81 and a manual switch 92 are connected in series with apower source 90. Therefore, when the timer knob is set at the startingposition, the cam switch 81 is closed first and a pilot lamp 93 islighted indicating that the washing machine has been placed inoperation. In this case, since no water is in the outer tank 8, thepressure switch is in NC position and the cam switch 83 in a position.Therefore, the filling solenoid valve 43 is energized to start filling.When the water filled in the outer tank 8 has reached a prescribedlevel, the pressure switch 45 is switched to NO position and the polechange motor 28 is actuated through a selective switch 94 and areversing switch 95, since the cam switch 86 is in a position. Theselective switch 94 is provided for the purpose of shifting the washingoperation from strong washing operation to mild washing operation orvice versa and is operated manually. The reversing switch 95 and anotherreversing switch 96 are provided to change the proportion of the periodof normal rotation to the period of reverse rotation of the motor 28.Thus, it will be understood that the motor 28 rotates in the normaldirection and in the reverse direction repeatedly in a predeterminedcycle, causing the drum 14 to rotate in the normal direction or in thereverse direction, whereby the clothing in the drum is rolled thereinand thus washed. In the process of the washing operation, the timermotor 89 rotates to carry out the'program, since the cam switch 87 isheld in a closed pos1t1on.

Upon completion of the washing process, the cam switch 82 is closed, andthe cam switch '83 is brought into b position and the cam switch 84 intob position, so that a drain valve 75 is opened to drain the washingwater and at the same time a microswitch 76 is closed which isoperatively associated with said drain valve 75. Upon completion of thedrain, the cam switch 83 is brought into a position to actuate thefilling solenoid valve 43 and thus filling is commenced. When the waterin the outer tank 8 has reached the prescribed level, the pressureswitch 45 is shifted from NC position to NO position, whereby filling isinterrupted. The timer motor 89 and the motor 28 continue to rotate inthe period from the drain process to the filling process and thereforethe drum 14 rotates continuously at the same speed as in the washingprocess.

Upon completion of a rinsing operation for a predetermined period, thewashing machine enters the spinning process. In this case, the camswitch 73 is closed and the cam switch 87 is opened, so that the timermotor 89 is stopped and a voltage is impressed on the vibrationdetecting circuit shown in FIG. 6. At the same time, the cam switch 186is brought into b position, so that the motor 28 starts to rotate in onedirection at the same speed as in the washing process.

Here, the movement of washing in the drum will be described. Firstly, aclothing thrown into the drum settles in the bottom of the drum but whenthe drum starts rotating, the clothing is carried upward by the bafliesand drops gravitationally from a certain height. The distribution of theclothing in the drum is not always the same, namely the clothing Imay bein the form of a mass at one time and may be in the form of a relativelylong web at another time. When the clothing is in the form of a web andextends longitudinally along the peripheral inside surface of the drum,it is relatively distributed evenly with respect to the center ofrotation of the drum.

The distribution becomes extremely uniform particularly when arelatively large quantity of clothing is placed in the drum, because theclothing is distributed along the peripheral wall of the drum in anannular shape.

However, the condition of clothing distributed evenly with respect tothe center of the drum does not last long and in several to several tensseconds the clothing distribution becomes random again, with ununiformdistributing. The condition of clothing distributed evenly with respectto the center of the drum appears repeatedly at relatively longperiods.' A

It will be appreciated, therefore, that if the drum is acceleratedrapidly to create in the clothing such a large centrifugal force as tokeep it attached on the inside wall of the drum, under the conditionwherein the distribution of the clothing with respect to the center ofrotation of the drum is uniform, the amplitude of vibration of the drumin the process of acceleration and spinning will become small. Thepresent invention is characterized in that whether the clothing in thedrum is uniform distribution or not is acknowledged by detecting theamplitude at which the outer tank is vibrating, so that acceleration ofthe drum may be effected when the distribution of the clothing isuniform.

Namely, as shown in FIG. 5, the movable contact 55 is connected to theouter tank suspending bolt 4 through the vibration transmitting rod 52and the fixed contacts 56 are arranged in opposed relation to saidmovable contact. Between the movable and fixed contacts is provided aspacing S.

With the vibration detector of the arrangement described, when the drum4 vibrates with a vibration wave form as shown in FIG. 9 and if theamplitude of the vibration exceeds a predetermined value, the movablecontact 55 is brought into Contact with the fixed 6 contact 56 andperforms an ON-OFF operation in the same cycle as the cycle in which thedrum vibrates.

In this case, since the condenser 64, provided in parallel to themovable and fixed contacts, discharges the electric charge storedtherein through said movable and fixed contacts, the base potential ofthe transistor 65 does not rise to a level to energize said transistor,so that the transistor 65 remains deenergized and the relay is heldinoperative with no current owing through the exciting coil thereof.

However, when the clothing in the drum is in a relatively uniformdistribution with respect to the center of rotation of the drum, thedrum vibrates at a small amplitude and therefore the movable contact andthe fixed contact 56 of the vibration detector are held disengaged overa certain period of time. As a result, the voltage of the condenserreaches a level to energize the transistor 65 and thus the transistor 65is energized. Upon energization of the transistor 65, a current flowthrough the exciting coil 72 of the relay through the followingtransistor 66, and a contact 79 and a contact 78 provided in series withthe timer motor 89 are actuated, whereby the pole of the motor 28 ischanged to drive the drum 14 at Va rate twice as high as that in thewashing process. At the same time, since the contact 78 is actuated, thetimer motor 89 is actuated again to control the cam switches. Uponpassage of a predetermined time after the pole of the motor 28 ischanged, the cam switch is brought into b position, so that the motor 29is set in motion, and at the same time the cam switch 87 is closed andthe cam switch 73 is opened. The contacts 78 and 79 of the relay arereturned to the position shown and the `motor 28 is shifted to low speedrotation.

Since the rotation of the motor 28 is transmitted to the driving shaftof the motor 29 through the overrunning clutch 31, slippage occurs atthe clutch 31 when the motor 28 is set in motion and thus the drum 14 isdriven from the motor 28.

Therefore, by employing a 4 pole-2 pole pole change motor for the motor28 and a 2 pole motor for the motor 29 and by suitably selecting thereduction ratio from the rotary shaft of the motor 28 to the rotaryshaft of the motor 29 and the reduction ratio from the rotary shaft ofthe motor 29 to the drum shaft 12, it is possible by the above-describedoperation to accelerate the rate of rotation of the drum stepwise fromthe rate of rotation in the washing process to the final rate ofrotation in the spinnlng process.

Now, the vibration characteristics of the moving parts, such as theouter tank 8, the drum 14 and the motors 28, 29, resiliently suspendedfrom the outer frame by four suspension springs 7, will be discussed.

The vibration of the mass system suspended by the springs is composed ofa component in a vertical plane and a component in a horizontal plane,and the natural frequency thereof is generally higher in the verticalplane than in the horizontal plane. This is because, while the naturalfrequency of the vibration in a horizontal direction is determined bythe distance from the semispherical concaved surface 3 to the center ofgravity of the resiliently supported moving part, that of the vibrationin a vertical direction is determined by the mass of the resilientlysuspended moving part and the spring constant of the four suspensionsprings. The springs are naturally required to be large in springconstant or large in rigidity because they must support the mass system.In practice, the vibration has a characteristic as shown in FIG. 10.

With such vibration characteristic, when the vibration of the drumcoincides with the natural frequencies in a horizontal and a verticaldirections, the amplitude of the vibration becomes large even if thevibrating force, that is, uniform distribution, is small. Thus, it willbe appreciated that the period wherein the frequency of the drumcoincides with the natural frequency thereof must be made as short aspossible.

On the other' hand, the cycle of vibration of the drum substantiallycoincides with the cycle of rotation of the drum. Therefore, it will beunderstood that a great vibration preventing effect will be attained bysetting the rotating speed of the drum such that the aforesaid periodwherein the frequency of the drum coincides with the natural frequencythereof in a horizontal and in a veltical direction, may be minimized.

Namely, with reference to FIG. 10, wherein reference character f1represents the frequency in the washing operation, f2 the frequency atan intermediate rate of rotation in the process of acceleration from thewashing operation to the spinning operation, f3 the frequency at thefinal rate of rotation in the spinning operation, fnh the naturalfrequency in a horizontal direction and fnv the natural frequency in avertical direction, the vibration of the drum can be effective bysetting the rotating speed of the drum such that f1, f2 and f3 may notcoincide with fnh and fm, as shown.

In other words, if the natural frequency fnh in a horizontal directionis located between f1 and f2 and the natural frequency fnv between f2and f3, the frequency of the drum will pass the points of these naturalfrequencies instantaneously during the process of acceleration and moveup to a higher level before the amplitude of the drum becomes large.

The present invention will be further described with reference toanother embodiment thereof. In the present invention, it is essential todetect the amplitudes of the drum 14 and the outer tank 8 as accuratelyas possible. Particularly, the detector is required to be accurate inoperation, long in service life and low in cost.

In the embodiment shown in FIG. 7, use is made of a piezo element fordrawing a vibration, propagating to the suspension springs 7, in theform of an electric signal and a relay is actuated when said electricsignal is below a predetermined value over a predetermined period,whereby the pole change of the motor 28 is effected.

In FIG. 7a, pressing member 99 is disposed for engagement with the bolt4 through a lever 98 and a piezo element 100 is interposed between thepressing member 99 and the stay 2. A lead wire 101 of the piezo elementis led into the control box 50 and connected with the control circuittherein. The control circuit, in this case, is arranged as shown in FIG.8 and operative in such a manner that the electric signal from the piezoelement is amplified for comparison with a reference value and when theformer is greater than the latter, that is, when the frequency of thedrum is greater than a tolerance, the relay is held inoperative, whereaswhen the former is Smaller than the latter, the relay 72 is actuated,thereby accelerating the drum.

The foregoing description has been made with reference to the casewherein the clothing in the drum is distributed substantially evenlywith respect to the center of rotation of the drum during the washingoperation of the drum rotating at a low speed, and such distribution ofthe clothing is maintained in the process of acceleration. However, itis probably, though very rarely, that the uniform distribution isdisrupted in the process of acceleration. This is attributed to the factthat the washing which has been located in the proximity of the centerof rotation of the drum during the low speed rotation of the drum, isnot moved radially uniformly and concentrated locally during itsdisplacement toward the peripheral wall of. the drum under the influenceof centrifugal force in the process of acceleration.

If ununiform distribution occurs in the process of acceleration in themanner described, the vibration of the drum becomes large abruptly andthe amplitude of the vibration detected by the detector exceeds thetolerable limit, with the result that the current supply to the relay 72is interrupted again. Therefore, the relay contact 96 is automaticallyreturned to its original position and the drum 14 resumes the low speedrotation at which it was CJI driven in the washing process and maintainsthe same ro-' tation until the amplitude of vibration becomes smallerthan said tolerable limit. Such an excessively large vibration tends tooccur in the initial stage of acceleration and will not occur under thecondition wherein the clothing is completely attached to the peripheralwall of the drum. Therefore, to avoid such vibration, it is onlynecessary to hold the cam switch 73 in its closed position only for theperiod of acceleration of the drum from a low speed rotation at the timeof completion of the spinning to the next intermediate rotation.

Upon completion of the spinning, filling takes place for rinsing. If, inthis case, a water level selecting switch 102 is in a closed position,the filling goes on superfiuosly just for that period when the camswitch 84 is held in a position, even if the pressure switch 45 isswitched from NC position to NO position, and accordingly, rinsing iseffected with a larger amount of water than in the washing process,

Finally, spinning is performed. In this case also, the speed of rotationof the drum is shifted to a higher level by means of the amplitude ofthe drum as mentioned previously. The motor 29 will not be set in motionwhen a spinning force adjusting switch 103 is set in an open position,and the drum 14 is driven at a higher speed of rotation of the motor 28to effect a mild spinning.

When the switch 103 is set in a closed position, on the other hand, thedrum is driven from the motor 29 at the final high speed, so that astrong centrifugal spinning can be attained. It is to be understood thatin shifting the drum from the rotation for washing operation to the nexthigher speed rotation, the speed of rotation of the drum may be changedby varying the transmission gear ratio of a speed change gear, such as avariable pulley, in addition to changing the poles of the motor.

We claim:

1. A washing machine comprising means for detecting a vibration of aclothing accommodating drum and for driving said drum at a relativelylow speed rotation and a relatively high speed rotation, whereby therotating speed of said drum is shifted to the high speed rotation whenthe amplitude of vibration of the drum during rotation at the low speedis held not greater than a tolerable value over a predetermined period.

2. A washing machine as defined in claim l, wherein there is providedmeans for driving the clothing accommodating drum at at least twodifferent speeds of rotation and the natural frequencies of resilientlysupported parts, including said drum, are located between said speeds ofrotation.

3. A washing macltine comprising means for driving a clothingaccommodating drum at three or more different speeds of rotation, andthree different speeds of rotation being located at points outside thenatural frequencies of resiliently supported parts including said drum,the speed of rotation of said drum being shifted from the lowest speedto the next higher speed only when the amplitude of said drum is heldnot greater than a tolerable value over a predetermined period and thesubsequent shifting of the speed of rotation and said drum to higherspeeds being effected automatically.

4. A washing machine as defined in claim 3, wherein a pole change fordriving the drum at two different speeds of rotation and another motorfor driving the drum at a higher speed of rotation than said speeds areconnected to the drum through an overrunning clutch.

5. A washing machine comprising means for detecting a vibration of suchparts as a drum and an outer tank resiliently suspended from an outerframe through suspension springs in the form of displacement of avibration transmitting rod connected to said suspension spring at thejoint between said suspension spring and said outer frame and means forcontrolling the speed of rotation of said drum in response to a signalfrom an electric contact mechanically operated by the displacement ofsaid vibration transmitting rod.

6. A washing machine comprising a piezo element adapted to detect achange in a tension developed in a suspension spring in accordance witha vibration of a drum and means for shifting the speed of rotation ofsaid drum from a low speed rotation to a higher speed rotation when theoutput of said piezo element becomes lower than a set value.

7. A washing machine as dened in claim 6, wherein said piezo element todetect the vibration of the drum is interposed between a bolt connectingthe suspension spring to an outer frame and a frame,

8. A washing machine comprising means for driving a drurn at at leasttwo different speeds rotation consisting of a low speed rotation and ahigh speed rotation, means for detecting a vibration of said drum duringthe low speed rotation of the drum and in the process of acceleration ofthe drum from the low speed rotation to the high speed rotation, andmeans for accelerating the drum to the high speed rotation when thevibration of the drum detected by said vibration detecting means isbelow a tolerable value and returning the drum to the 10W speed rotationagain when the amplitude of vibration of the drum becomes excessivelylarge in the process of acceleration.

9. A washing machine/comprising a pole change motor for driving a drum,a relay for changing the pole of said motor and vibration detectingmeans for detecting the a-mplitude of vibration of said drum and therebycontrolling said relay, said relay being actuated to change the pole ofsaid motor when said amplitude of vibration of the drum is held below atolerable value over a predetermined period.

References Cited UNITED STATES PATENTS 2,296,261 9/ 1942 Breckenridge etal. 68-23.1 2,832,208 4/1958 Stone 68-23.1 3,114,705 12/1963 Pribonic etal 6-8-23.1X 3,268,791 8/1966 Burns et al 68-23.1X 3,273,361 9/1966Smith 6823.1X 3,283,547 11/1966 Severance 68-23.1X 3,311,237 3/1967Bergeson et al 68-23.1X

WILLIAM I. PIRICiE, Primary 'Examiner U.S. Cl. XJR. 210-144

